Line identification circuit for



July 10, 1951 w. H. T. HOLDEN ET AL 23388 LINE IDENTIFICATION CIRCUITFOR TELEPHONE SYSTEMS '7 Sheets-Sheet 1 Original Filed Sept. 20, 1940 Y9 M N R 3 M m 5 LS T 0/ A I HW i {1 $9 TL H v i W 3E W I. v =3 m :5 m mA k at w 6R W M W mmww o mk 5E0 E 06 N GK 3 GR M W M m at #9 MW A l 3 a3 I h H |l lllllAU U \J U D Ululll DlT U D U) LU )l w 3 4% sq GPQN 4mm Qw w 6Q July 10, 1951 w. H. T. HOLDEN ET AL 23,338

LINE IDENTIFICATION CIRCUIT FOR TELEPHONE SYSTEMS Original Filed Sept.20, 1940 'T Sheets-Sheet 2 lNVEA/F'ORS W HOLDEN B. F LEW/5 A? A rfoam/5v y 1951 w. H. T. HOLDEN ET AL 23,388

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I4! H. Z HOLDEN m/vEg/yrons a E EMS b Qk A r TORNE Reissued July 10,1951 LINE IDENTIFICATION CIRCUIT FOR TELEPHONE SYSTEMS William H. '1.Holden, Woodside, and Benjamin F. Lewis, Bay'side, N. Y.-, assignors toBell Telephone Laboratories, Incorporated, New York, N. Y., acorporation of New York Original No. 2,284,870, dated June 2, 1942,Serial No. 357,520, September 20, 1940. Application for reissue May 17,1950, Serial No. 162,576

Matter enclosed in heavy brackets I: 1 appears in the original patentbut forms no part of this reissue specification; matter printed initalis indicates the additions made by reissue.

11 Claims.

This invention relates to telephone systems and more particularly tothose systems in which the numerical indication of a calling line isautomatically determined and made available.

It is Well. known that in certain types of telephone connectionssuch asthose, for instance, in which the calling line isextended automati callyor otherwise to some remote station, it is sometimes necessary toascertain the number of the calling station in order that charges forthe call may be properly assessed to said station. Such connections areknown as toll or long distance connections and in some types ofautomatic telephone systems in which the calling line is routed to itsdestination via the position of a recording. operator where, after thenumber has been communicated to the operator by the calling subscriber,said number is verified over a socalled checking multiple. Thisverification is made by touching the tip of a checking cord to a pin inthe checking multiple that is assigned to the given number and ifthenumber as given by the calling party is correct, a tone circuit iscompleted over the checking cordwhich is heard in the operatorstelephone set. On the other hand, if the number as given does notcorrespond to that of the pin to which the tip of the checking cord istouched, the tone circuit is not completed, which fact indicates to theoperator that the number given by the calling party does not correspondto that of the station from which he iscalling and service may then bedenied until the discrepancy is rectified.

In automatic telephone systems, it is desirable to have the identity ofthe calling station ascertained and transmitted automatically to somepoint at which it may be recorded on settable registers for the visualdisplay of the number, if the call is ccunpleted through an operatorsposition, or for automatic recording if the information is to beutilized for operating printing or other recording devices responsive tothe setting of the registers.

Our invention is principally concerned with the automatic identificationof the calling line number, and its principal feature is an arrangementof two main groups of electronic devices provided with multicontrolelements which, when operated, produce two coordinate translations, onefor each two digits of the line number, each of which may then besuitably resolved into a single translation for each digit. Similaridentifying arrangements are utilized in the then copending applicationof W. A. Rhodes Serial No. 357,518, which issued as Patent No. 2,267,950on December 30, 1941, and the copending application of [W. A] H. M.Bascom et a1. Serial No. 357,519 which issused as Patent No. 2,270,246

on January 20, 1942, both of said copending lapplicatio-ns having beenfiled on September 20, 1940.

Another feature of our invention is an arrangement of four auxiliarygroups of electronic deivces which, operating in conjunction with thoseof the two main groups, resolve the twodigit translations made by eachmain group of devices into single-digit translations, one for each digitof the line number.

According to one embodiment of the invention as adapted to provideidentification for each of the lines of a ten thousand-line telephoneoffice and in which the electronic devices employed are of the so-calledcold cathode gas-filled type well known in the art which break down andbecome conducting upon the application of a critical or breakdownpotential to a control anode, we propose to use two main groups of onehundred such cold cathode tubes each having one hundred control orstarting anodes with each line to be identified connected to a startinganode in a tube of each group, and four auxiliary groups of ten coldcathode tubes each having ten starting anodes with each cathode of amain tube connected to a starting anode in a tube in each of twoauxiliary groups. Upon the application of a distinctsignaling voltage toany one of the lines, the

two tubes in the main groups having, respectively, one of their startinganodes connected to the line become conducting, and their conductionimmediately activates each of the four tubes in the auxiliary groupshaving anodes connected to the cathodes of the two conducting tubes inthe main groups. Since each of the auxiliary tubes bears a digitalcoordinate relation to its associated main tube, there is present in thefour operated auxiliary tubes four distinct signals each of whichdesignates a digit of the line number. These signals may, of course, bereceived upon suitable registers from which the number may then bedisplayed or recorded by appropriate apparatus provided for the purpose.

A clearer conception of the scope and purpose of the invention may beobtained from the following description, taken in connection with theappended claims and attached drawings, in which Fig. 1 shows a schematiclayout of an automatic telephone line extension in a telephone system ofa well-known type;

Fig. 2 shows, in part, one of the two main groups of tubes;

Fig. 3 shows, in part, the two auxiliary groups of tubes which areoperatively associated with the main group of tubes shown in Fig. 2

Fig. 4 shows the digit registers;

Fig. 5 shows, diagrammatically, the switching circuit, the progresscircuit and the printer;

Fig. 6 shows, in part, the other of the two main groups of tubes;

Fig. '7 shows, in part, the other two auxiliary groups of tubes whichare operatively associated with the main group of tubes shown in Fig. 6;while Fig. 8 shows the manner in which Figs. 1 to 7, inclusive, shouldbe arranged with respect to each other'in order to disclose theinvention.

Referring now, to the drawings, there are provided as indicated thereinone hundred tubes, namely tubes 00 to 99, inclusive, for the thousandsand hundreds digit designations of the various ones of the ten thousandline[s] numbers in a telephone ofiice and one hundred other tubes,namely, 600 to 699, inclusive, for the tens and units designations ofsaid line[s] numbers. Each tube in each group has one hundred and twoelements, namely, a main anode indicated by an arrowhead within the tubeenvelope and connected to conductor 242, a main cathode indicated by along slender rectangle within the tube envelope each connected to asource of negative potential, and one hundred starting anodes indicatedas short lines perpendicular to the cathode within the tube envelope.There are, therefore, twenty thousand main tube control anodes for theentire circuit.

Each line is provided with an identifying conductor, preferably anextension of its sleeve as, for instance, conductor H9, and thisconductor is connected to a punching on the terminal assembly block TABIwhich is assigned to the line correlated to the identifying conductor.Thus in Figs. 1 and 2, conductor 9 is connected to terminal punchingl9l9, and line A is assumed to have the same numerical designation asthe punching. It will be observed that the terminal assembly block TABIis arranged in vertical sections of one hundred punchings to thesection, there being, for a ten thousand line ofiice, one hundred suchsections with each section allocated to a particular group of onehundred lines to the punchings of which are connected the sleeve ex- 4 ltensions of the related lines, in the same manner as already describedfor line A (l9l9).

From the other side of the punchings of TABI extend two parallelconductors, one to a control anode in one of the one hundred tubes 00-99and the other to a control anode in one of the one hundred tubes 600-699the latter conductor via a punching on terminal assembly block TABIIwhich is identical in structure and arrangement to TABI. The tube ineach group to which each of said conductors is connected depends, in thecase of the first group of tubes 00-99, upon the thousands and hundredsnumerical designation of the line and, in the case of the second groupof tubes 600-699, upon the tens and units designation of [the line] saidnumerical designation. Furthermore, since, as a matter of convenience,the one hundred control anodes in each of the tubes of both main groupsof tubes are themselves numerically designated inconsecutive order, theparticular control anode in each tube to which each of the aboveconductors would be connected may be made to depend upon the identitybetween the numerical designation of the anode and the numericaldesignation of the two digits of the line number which are to beidentified by a tube in the other main group.

Thus, punching i9l9 on TABI which, on one side is connected to conductorH9 is connected on its other side to conductors 240 and 2. The line l9l9has a thousands-hundreds digit designation of "I9 and since tube [9 isreserved for the identification of the numerical designation of the onehundred lines in the ofiice bearing the thousands-hundreds designation19 conductor 240 is extended to a control anode in tube [9 and, viaresistance 244, particularly to the anode therein labeled [9; anode l9having been selected because it bears the same numerical designation inthe consecutive line-up of the hundred anodes of the tube as thetens-units designation of the line number. In the same way, conductor24! extends to terminal punching |9l9 in the terminalassembly blockTAB-11 and thence to a control anode in tube [I I9] 619, andparticularly to control anode l9 therein via conductor 24! andresistance 644'. Here again the particular anode in the tube selectedfor connection to conductor 24I may be determined as a matter ofconvenience by the thousands-hundreds designation of the line numberwhich, in the case of line number I9I9 (line A) happens to be the sameas the tens-units designation.

The identifying conductor of every line in each hundred line group ofthe one hundred such groups for a 10,000 line oiiice is thus similarlyextended, via a resistance, to a control anode in the particular tube inthe group of tubes 00-99 which is reserved for the thousands-hundredsidentification of that group and, via another resistance, to a controlanode in the particular tube in the group of tubes 600-699 which isreserved for the tens-units identification of that group. It is obviousthat the operation of a tube in each group, each having one of itscontrol anodes connected to the identifying conductor of a line.

through its extension from the punchings on terminal assembly blocksTABI and TABII may be used to operate auxiliary equipment and signalingapparatus that will identify the con- [ductor] ductor-s and, therefore,the line.

Since the operation of a tube in the main group of tubes 00-99 and theoperation of another tube in the main group of tubes 600-699 eases:

each identifies a pair of digits of the line: number, additionaltranslations are necessary in order to [trace back} resolve the identityof each of the four digits of which the line numberiscomposed. To carryout these translations, two auxiliary groups of ten ten-control anodetubes are provided for each main group of tubes 00-99 and 600-699, oneauxiliary group for each of the two digits decoded by a main group oftubes. These tubes are numbered 200 to 209, 2l0' to 219, inelusive, forthe group of thousands-hundreds tubes 00-99, and 220 to 229, and 230 to23-9, inclusive, for the group of tens-units tubes 600- 699. Thecathodes of the tubes in each of the main groups are connected tonegative battery through a high resistance, and conductors arebroughtfrom each of said cathodes to a start anode in a tube in each of theassociated auxiliary group. The order of connection is ten cathodes fromas many consecutively numbered tubes in a main group connected,respectively, to as many control anodes in a tube of one of theauxiliary groups, and each one of the same cathodes connectedrespectively to a control anode in each of the ten tubes in the otherauxiliary group. The reason for this is that, in the case of thethousands-hundreds digits, for example, the auxiliary group of tubes200-209 inclusive is used to identify the different thousands digits ofthe line numbers, and inasmuch as there will. be. a maximum of tendifferent numerical values of the hundreds digit for each numericalvalue of the thousands digit, the cathodes of the ten tubes which are toidentify the same thousands digit designation of. the line number ioreach different numerical value of the hundreds digit are connected to asmany control anodes in the same tube of the. auxiliary group 20.0-20.9and to a control anode in each of the ten tubes of the other auxiliarygroup 2l0-2l9, the selection of the tube. to whose control. anode thecathode of the main tube is to. be connected being determined, ofvcourse, by the correspondence of the. units. digit of the numerical.designation of the tube. in themain group andthat: of. the tube in theauxiliary group. In the same manner for the tens-units digits. Theauxiliary group of tubes 222-229, inclusive, is used to identify thedifierent tens digit of the line numbers, and inasmuch as there will bea maximum of ten different numerical values of the units digit for eachnumerical value of the [hundreds] tens digit, the cathodes of the tentubes which are to identify the same tens digit of the line number foreach diiferent numerical value of the [units] hundreds digit areconnected to as many control anodes in the same tube of the auxiliarygroup 220-229 [and to a control anode. in each of. the ten. tubes of theother auxiliary groupv 239-239,] In the same manner for the.identification of the ten diflerent values of the units-digit, thecathode in each of the main-group of tubes 600-699 identifymy the somenumerical value of the unit's digit being each connected toon anode: inthe one tube of the .auaziliarygroupof tubes 230-239 which is reservedfor the numerical value of said digit. In each case the selection of thetube in each group to one of whose control [anode] anodes the cathode ofthe main tube is to be. connected being determined, of course, by thecorrespondence of the tens and. [units] appropriate. digit of. thenumerical designation of the tube. in the main group and. that of the.tube in the auxiliary group;

6'. The following table: shows the distribution of connections.

l Connections to 1 we auxi my groups groups 00' 200 an d 210 01 200 and211 02 200 and 212 66 26631121 215 10. 201 and 210 11 201 and 211 13620s and 210 91 209 and 211 2?; 209 and 219 600 220 and 230 601 220 and231 66?; 220-and 239 610 221 and 230 611 221 and 231 i 221 and 239 620222 and 230 229 and: 238 699 229 and 239 Ill-1e anode voltage for alltubes is a superposed alternating current supplied by source 304connected to the primary of transformer. 30!] the secondary of which. isconnected to negatively grounded battery 306 and toconductor 242 whichconnects with all tube anodes. Preferably the source should bevoltsdirect current plus 70' volts alternating current corresponding toa peak value of 200 volts. With 80 volts drop in the glow discharge ofany of the tubes there will be a maximum of volts dur-- ing slightlymore than the positive half cycle of anode voltage across the cathoderesistances of the tubesin the main. groups, so-that there will be amplevoltage to operate the control gaps of the tubes in the auxiliarygroups. However, this is intended merely by way of illustration as it isobvious that the voltage values to be supplied cannot be fixed with anyconsiderable accuracy as they will depend upon the characteristics ofthe tubes used.

The cathode of each tube in each of the two auxiliary groups of tubes[21-0-2391 200-239 is connected to a contact of multicontaet relay 3Mwhile the armature making with said contact is joined to a winding of aregister relay. There is provided a register of ten relays for each ofthe digits tobe identified, namely, a thousands register comprisingrelays THU-TBS, a hundreds register comprising relays Hit-H9, a tensregister comprising relays Til-T9 and a units. register comprisingrelays U0-U9. Each. relay in each register is double wound with theright winding connected to an armature or said multicontact relay 3!,the connections to allrelaysbeing made consecutive in order to group therelays of each register with the cathodesof. the tubes of the particularauxiliary group that identifies the digit reserved-for the register;

cases Tables of codes Conductors grounded Register relay Digit operateddesignated The groups of five local conductors 400 -400 inclusive ofeach register are connected in consecutive order to the armatures of arelay 510, 511, 512, and 513, the make contacts of which extent to themagnets of any commercially available printer 505 via conductors400-404. Thus conductors 4001-4041 of the thousands register areconnected to the armatures of relay 510; those of the hundreds register4002-4042 are connected to the armatures of relay 511; those of the tensregister 4003-4043 to the armatures of relay 512 and those of the unitsregister 4004-4044 to the armatures of relay 513. These relays areoperated in a cyclical order by any suitable progress circuit 501 whichfirst operates relay 510 to connect conductors 4001-4641 of thethousands register to the printer 505; then operates relays 511, 512 and513 in the order given to connect, in succession, the signalingconductors of the other three registers operatively associated with theabove relays. Inasmuch as each register will have one of its relaysoperated at the time of the cut-through to the printer, as will beshortly described, the two conductors in the register group which aregrounded by said relay will cause the printer to operate and print thedigit designated by said grounded conductors.

Having described the structural arrangement of our invention, its mannerof operation when adapted to a specific type of telephone system willnow be set forth in some detail.

In Fig. 1 is shown a schematic disclosure of the equipment at theoriginating oflice of an automatic telephone system of, the so-calledstepby-step type wherein switching selectors, shown in the figure as 1stselector, 2nd selector, etc., are usually settable directly in responseto dial pulses from an originating station to reach the terminals of awanted station. In telephone connections involving the necessity ofidentifying the number of the calling station such as, forinidentification circuit, relay 106 will operate.

stance, long distance connections, the line is usu- 8, by this inventionis automatically connected to the trunk by any suitable means andproceeds with its operation of determining the number of the callingstation.

The line identification circuit is used in common by a group of trunksand, in its operation is, of course, used only by one trunk at a time,an interval during which other trunks await their turn in any desiredpreferential order for connection therewith to obtain similar lineidentification service. Connector circuits by which a common circuit isconnected to a plurality of individual circuits on a lock-out basis arewell known and numerous in the switching art. The connecting circuitshown in Fig. 1, therefore, is merely illustrative of a number of otherand similar connecting circuits which might be used.

We may now assume that station A, identified by line number 1919,initiates a call which requires line identification. When the variousselectors have been selectively positioned to engage a trunk on the 3rdselector bank, line relay of said selector operates over the line loop,causing thereby the operation of relay 101 over its lower contactswhich, in turn, completes a circuit for relay 103 which extends fromground on the right contacts of relay 101, right contacts of relay I05,winding of relay 103 to battery. Relay 103, upon operating, closes apath for relay 106 which extends from battery through the left outercontacts of relay 103, winding of relay 106, through the lowercontinuity contacts of relays 106106" which relays are identical withrelay 106 but individual to each of the trunks having access to theidentification circuit, to ground. If all the relays 100-106-106" arenormal, which indicates that no trunk is locked in with the On theotherhand, if one of said relays is operated, indicating thereby that atrunk is locked in with the identification circuit, then the abovecircuit will not be completed and relay 106 will not operate, in whichevent the connection will wait until the circuit is established.Assuming, however, that all trunks are disconnected from theidentification circuit, then relay I06 operates, locks itself to groundthrough its lower front contacts and completes an obvious circuit forrelay 101 which, upon operating, grounds conductor 100 and therebycauses the operation of relay 301, closes through release conductor 109to the winding of relay and completes a circuit for relay 104' whichextends from ground through the upper inner contacts of relay 10'1,inner contacts of relay 103, winding of relay 104 to battery. Relay I04operates and connects conductor 102 to the sleeve of the connection viathe left contacts of relay 101 and thence to identifying conductor 1 19of the line A.

Itwill be observed that while relay 105 is operated, other trunks mightcause their respective relays 106 to operate if they are located,electrically, to the right of relay 106. However, their operation willbe ineffective since it will not be possible to operate their associatedrelay I01 inasmuch as the circuit of this relay is controlled over achain connection to the left, back to the upper back contacts of relay106, which, being operated, opens the path of all other relays I0'1I0'l" except relay I01.

Conductor 102 which is now connected to conductor 119 via the sleeve ofthe selector train is connected to the secondary winding of transformer303 which has its other terminal connected to positive battery 305.Inasmuch as alternating current source 304 is connected to the primarywinding of transformer 303 and source 304' is connected to transformer300, and since grounded negative battery 305 is connected to thesecondary winding of transformer 303, a superimposed alternatingpotential is applied to conductor I02 (which is, of course, lower thanthe potential applied to the tube main anodes through transformer 300 ina conductor 242) and thereover via the sleeve of the selector train toconductor H9, punching l9l9 of terminal assembly block TABI, conductor240, resistance 244 to control anode 19 of tube l9 and, also, conductor2M, punching |9l9 of terminal assembly block TAB-II, resistance 644' tocontrol anode l9 of tube 6|9. It will be observed that grounded positivebattery through a resistance is connected to the cathode of each tube inthe groups -95 and 000-699. The difference of potential created by thesuperimposed positive voltage at anode l9 of tube I9 as traced theretofrom the primary of transformer 303 and the negative resistance batteryconnected to the cathode of tube I9 is sufiicient to break down thecontrol gap between the cathode and said anode. Similarly, thedifference of potential between anode l9 and the cathode of tube 619 issufficient to break down the control gap between the cathode and saidanode. Both tubes [9 and GIS, on being rendered conducting through thecontrol gaps thereof, immediately break down in their respective maingaps inasmuch as positive superimposed potential through the secondaryof transformer 300 is connected to the main anode of each of the tubesin the two main groups as already explained, and the difference ofpotential [created] established between the cathode and main anode ofthe two tubesl9 and (H9- upon the flow of current between theirrespective cathodes and one of the control anodes in each of the tubes,is such as to cause said tubes to break down in their respective maingaps and become conducting therethrough. 7

As already explained, the [main anode] cathode of each tube in the groupof tubes 00-99 is connected to a control anode of a tube in each of itsauxiliary groups of tubes 200-209 and 2l0-2I9. The same thing is true ofthe tubes in the group 600-099 in which the [main anode] cathode of eachtube is connected respectively, to a control anode of an appropriatetube in each of the two auxiliary groups of tubes 220-229 and 230-239 asalready described. In the case of tube l9, the [main anode] cathodethereof is connected to control anode IQ of tube 2M and to control anodeill of tube 2l9; in case of tube Hi9,

the [main anode] cathode thereof is connected to control anode 09 oftube 22! and to control anode 0! of tube 239. However, since relay 30!is operated, the cathode of each tube in all four auxiliary groups isconnected to negative battery through the operating winding of a relayin one of the numerical registers. Specifically, the cathode of eachtube in the group 200-209 is connected to negative battery through thewinding of one of the relays of the thousands register, the cathode ofeach tube in group 2l0-2l9 is connected to battery through the windingof one of the relays in the hundreds register, the cathode of each tubein group 220-229 is connected to battery through the winding of one ofthe relays in the tens register and the cathode of each tube in group230-239 is connected to battery through the winding of a relay in theunits register.

In tube 20 I, the difierence [of] in potential between [that on] controlanode l9 and [that on] the cathode of the tube, applied thereto bygrounded positive battery through the winding of relay THI, issuflicient to break down the control gap of the tube thereby causing itto become conducting therethrough, and the flow of space current createdthereby establishes a sufiicient potential diiierence between thepotential on the cathode of the tube and the superimposed alternatingpotential, applied to its main anode via conductor [202,] 242 throughthe secondary winding of transformer 300 as to cause the tube to ionizeits main gap and produce a flow of current through the main anode andcathode paths. Since relay 'IHl is included in this circuit path, saidrelay now operates over its right winding and looks over its leftwinding and contacts to ground on the contacts of relay 505.

In the same manner as above described, tube 2!!! isrendered conductingto cause the operation of relay H9 in the hundreds register; tube 22l isrendered conducting to cause the operation of relay Tl in the tensregister and tube 239 is rendered conducting to cause the operation ofrelay U9 in the units register. These relays operate over theirrespective right windings and lock over their respectiveleft windingsand contacts to ground on the contacts of relay 505. It will be notedthat the above relays, when operated, register the number l9l9 which, asabove described, is the line number of the calling station A.

Relays THI, H9, TI and U9 all apply ground to the common conductor 400which connects with the winding of the start relay 500 in the progresscircuit, and causes said relay to operate and start the operation ofsaid progress circuit, which may be of any suitable design, to completecircuits (not shown) whereby relays 510, 5i i, 512 and 5|3 are operatedin the order given and whereby the succeeding relay is not operateduntil the preceding one is released, and whereby the interval duringwhich each of said relays is maintained in an operated position issufficient to cause the performance of the registering or recordingfunctions indicated below.

The apparatus supplied to receive the signal grounds applied to the fourdifferent groups of conductors 400404- inclusive by the operation of arelay in each of the digits registers depends upon the kind of anindication of the calling number desired, as it is evident that anysettable device adapted to record or register the application of groundsto said conductors and translate them into a visual, oral or recorded[resignation] designation of the calling number, will do. In thedescription of the invention herein given, merely by way of illustratingits operation, it is assumed that a permanent record of the calling linenumber is desired and that this record is to be a printed one which canbe produced by any commercially available printer 506. When, therefore,relay 5l0 operates in preparation to record the thousands digit, anobvious circuit is closed for start relay 5l5 in the printer 506. Relay5l5 operates to prepare the printer to receive the signal grounds onconductors 402i and 4041 of the thousands register via the contacts ofrelay 5l0 and conductors 4024M, which grounds cause the operation oftwo'corresponding printer magnets upon the operation of which thethousands digit l (according to the above table) is printed.

Following the release of relay 510 by the progress circuit, the startrelay 5I5 also releases to restore the printer. Upon the operation ofrelay store the registers to normal.

| I, the five signaling conductors 4002-4042 of the hundreds registerare connected to the printer via conductors 400-404 and another obviouscircuit is completed for start relay 5I5 whereupon the printer is causedto repeat the above operations for printing the hundreds digit 9 inresponse to ground upon conductors 40I2 and 4022 of said hundredsregister.

'digit 9 are printed in response to ground on conductors 4023 and 4043in the tens register and conductors 40l4 and 4024 in the units register.

When the entire number has been printed,

contacts 5I6 are momentarily closed in the printer whereupon an obviouscircuit is closed for slow-release relay 505 which operates to removelocking ground from the relays locked in the registers, causing saidrelays to release and re- Relay 505 also connects ground to conductorI09, completing 'thereby a circuit for relay I05 which extends fromground on said conductor, top outer contacts of relay I01, winding ofrelay I05 to battery. Relay I05 operates, opens the circuit of relay I03which releases, in turn releasing relay I04 which disconnects conductorI02 from the sleeve of the connection and applies ground thereto inorder to provide a busy test of the I trunk for hunting 3rd selectors,Relay I03 fur-:

ther opens the circuit of relay I06 which, upon releasing, releasesrelay I01 which then releases relay 30I thereby disconnecting thecathodes of the tubes in the auxiliary groups from the relays of thevarious registers and further restores the 'functions for restoring thetrunk connector to normal. The release of relay 30I opens the cathodecircuits of tubes 20I, 2I9, 22I and 239, respectively, causing saidtubes to restore.

The removal of the signaling potential from conductor II9 also causesits removal from the control anode IQ of tube I9 and from control anodeIQ of tube BI9. These two tubes, with the controlling voltage removed,will now remain conducting only so long as the main anode voltage,applied through transformer 300, is on the positive half cycle of thevoltage induced by source 304. When the voltage reverses and negativevoltage is thus applied to the main anodes of these two tubes, they willcease to conduct and restore to normal. The identification circuit isnow normal in all its parts and may again be reseized for identificationoperations by other trunks.

One feature of this invention has not been mentioned before because itcould not be understood without a description of the invention. It

is the immunity of the identification circuit to false operations whichmay result from the presence of transients in the sleeve conductors ofthe various lines and, therefore, upon their respective identifyingconductors. In telephone ofiices such transients, due' to variouscauses, are always present and while they are not of sufficientmagnitude to cause the operation of electromagnetic apparatus connectedthereto, may still be of sufficient magnitude to break down the controlgap of a tube in each main group and thereby produce in consequence theseries of operations described above that would result in a line[display] recording even though the [lines] line concerned would not becalling. In our invention, however, the tubes would operate if the mainanode potential were on the positive half cycle of generator 304' at thetime the transient occurs. But the tubes would quench immediately whenthe generator advanced to the negative half cycle and thus restore thecircuit to normal before the tube operations could be registered in therelays of the digit registers.

While we have described the principle of our invention in connectionwith its specific application to a particular type of telephone systemand to a specific arrangement of gas-filled devices, itis to beunderstood that various other applications and embodiments thereof maybe made by those skilled in the art without departing from the spirit ofthe invention as defined within the scope of the appended claims.

What is claimed is:

1. A calling line identification circuit for the lines of a telephonesystem comprising a plurality of electronic devices having controlelements connected to said lines according to their numericaldesignation, and means responsive to the application of a potential tothe control elements connected to one of said lines for operating theassociated electron devices to indicate the identity of the line.

2. An identification circuit for the lines of a telephone systemcomprising in combination a plurality of electronic devices disposedcoordinately relative to the lines of a telephone system, and meanswhereby a potential applied to any one of said lines causes theoperation of any two of said devices in coordinate relation to eachother to identify the line to which said potential was applied.

3. An identification circuit for the lines of a telephone systemcomprising in combination two groups of electronic devices disposedcoordinately relative to the numerical designations of the lines of thesystem, means for applying a signaling potential through one of saidlines when calling to an electronic device in each group whereby saiddevices are rendered conducting, and other electronic devices responsiveto the conduction of said devices for identifying the numericaldesignation of said calling line.

4. A calling line identification circuit for the lines of a telephonesystem comprising two main groups of electronic devices having controlelectrodes connected to said lines, two auxiliary groups of electronicdevices for each of said main groups of devices having controlelectrodes connected to the cathodes of the devices in the associatedmain group, means responsive to the application of a potential to thecontrol electrodes of the devices in the two main groups for .operatingsaid devices whereby a potential is produced and applied to the controlelectrodes in the associated devices in the auxiliary groups,

and means responsive to the application of said potential to saidelectrodes for operating the devices in the auxiliary groups to indicatethe identity of the line.

5. A calling line identification circuit for the lines of a telephonesystem comprising in combination two main groups of electronic deviceshaving control electrodes connected to said lines, two auxiliary groupsof electronic devices for each of said main groups of devices havingcontrol electrodes connected to the cathodes of the devices in theassociated main group, means responsive to the application of apotential to the control electrodes of the devices in the two maingroups for operating said devices whereby a potential is produced andapplied to the control electrodes in the associated devices in theauxiliary groups, and circuit closing means including settable registersavailable at said associated devices for operating said devices andsetting said registers to indicate the identity of said line.

6. A calling line identification circuit for the lines of a telephonesystem comprising in combination two main groups of electronic deviceshaving control electrodes connected to said lines, two auxiliary groupsof electronic devices for each of said main groups of devices havingcontrol electrodes connected to the cathodes of the devices in theassociated main group, means responsive to the application of apotential to the control electrodes of the line initiating a call forcausing the associated electronic devices to become conducting, andmeans responsive to the operation of said devices for operating four ofthe devices in said two auxiliary groups for identifying the callingline to which said potential was applied.

7. An identification circuit for the lines of a telephone systemcomprising in combination an identifying conductor for each line, twogroups of electronic devices disposed in coordinate pattern in relationto the numerical designation of each of the lines in the system, eachelectronic device in each group having a plurality of startingelectrodes connected to as many line identifying conductors foridentifying two digits of the associated line number, means for applyinga signaling potential to the identifying conductor of one of said lineswhen calling and therethrough to the starting electrode in a device ineach group connected thereto, whereby said devices are renderedconducting, and other electronic devices responsive to the conduction ofsaid devices for identifying the numerical designation of the line towhose identifying conductor the signaling potential was applied.

8. An identification circuit for the lines of a telephone systemcomprising in combination with an identifying conductor for each line,a, first pair of electronic devices for a group of said lines, each ofsaid devices having a starting electrode for each line in the groupconnected to the identifying conductor thereof, a second pair ofelectronic devices for each device in said first pair of devices, eachhaving a starting electrode connected to the cathode of a device in saidfirst pair, means responsive to the application of a signaling potentialto the identifying conductor of a calling line in the group and,therethrough, to the start electrodes of the first pair of devicesconnected to said conductor, for operating said pair of devices, meansresponsive to the operation of said first pair of devices for operatingeach of said second pair of devices, and means responsive to theoperation of each of said second pair of devices for identifying theconductor to which said signaling potential was applied.

9. A calling line identification circuit for a group of lines, each ofsaid lines having a designation consisting of a plurality of symbolsdivided into groups, comprising a group of thermionic devices for eachgroup of symbols, there being in said thermionic devices as many controlelements therefor as there are symbols in the group, the number of saidelements in any one device being a multiple of the number of lines insaid group of lines, an identifying conductor for each line extending toa control element in each group of devices in accordance with the symbolidentit of its associated line, means for connecting a potential to theidentifying conductor of a, calling line in response to which thethermionic devices connected to said conductor are rendered conducting,and operative means included in the cathode circuit of said conductingthermionic devices for marking the designation of said calling line.

10. A calling line identification circuit for the lines of a, telephoneoflice comprising a plurality of thermionic devices having controlelements connected to said lines according to their numericaldesignation, each of said thermionic devices having a source ofalternating potential applied to their respective anodes, settableregisters selectively connectable to said thermionic devices, whenoperated, and means responsive to the application of a potential to thecontrol elements connected to one of said lines for operating theassociated thermionic devices whereby said registers are renderedsettably responsive to said operated thermionic devices for recordingthe identity of the calling line.

11. A calling line identification circuit for the lines of a telephoneofilce comprising a plurality of thermionic devices having controlelements connected to said lines according to said numericaldesignation, each of said thermionic devices having a, source ofalternating potential applied to their respective anodes, settableregisters se lectively connectable to said thermionic devices, whenoperated, and means responsive to the application of a potential to theelements connected to one of said lines for operating the associatedthermionic devices whereby said registers are not connected. to saidoperated thermionic devices if said potential is not sustained at saidelements during the negative half cycles of said source of alternatingpotential connected to the main anodes of the operated thermionicdevices.

WILLIAM H. T. HOLDEN. BENJAMIN F. LEWIS.

REFERENCES CITED The following references are of record in the file ofthis patent or the original patent:

UNITED STATES PATENTS Number Name Date 2,023,589 Hersey Dec. 10, 19352,267,950 Rhodes Dec. 30, 1941

